Map Sapling Learning A young researcher was evaluating a standard method for det

Question

Map Sapling Learning A young researcher was evaluating a standard method for determining the methylmercury content in blue fin using high performance liquid chromatography (HPLC). She determined the standard deviation (s) for the method to be 0.39 and assumed that s was a good approximation of 0. As a test, she used this method to evaluate the methylmercury content in a National Institutes of Standards and Technology (NIST) standard and determined the unknown amount to be within 0.16 ppb (U) of the known mean with 99% probability. How many replicate measurements of the NIST standard did the researcher perform? Number

Explanation / Answer

Apply:

Error = Z*Sigmax/ (sqrt(n))

so

solve for n

for this case..

alpha = 1-0.99 = 0.01

then

alpha /2 = 0.01/2 = 0.005

that will have a Z value of

Z = 2.57

then

if we want

error = 0.16

and sigma x = 0.39

n = (2.57*0.39/0.16)^2

n = 39.2423

roundup

n = 40

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